correct version detection of the Apple Xcode 4 clang compiler.

git-svn-id: http://root.cern.ch/svn/root/trunk@38419 27541ba8-7e3a-0410-8455-c3a389f83636

Makefile

@@ -394,6 +394,11 @@ CXXOUT ?= -o # keep whitespace after "-o"
 ifneq ($(findstring clang,$(CXX)),)
 CLANG_MAJOR  := $(shell $(CXX) -v 2>&1 | awk '{if (NR==1) print $$3}' | cut -d'.' -f1)
 CLANG_MINOR  := $(shell $(CXX) -v 2>&1 | awk '{if (NR==1) print $$3}' | cut -d'.' -f2)
+ifeq ($(CLANG_MAJOR),version)
+   # Apple version of clang has different -v layout
+   CLANG_MAJOR  := $(shell $(CXX) -v 2>&1 | awk '{if (NR==1) print $$4}' | cut -d'.' -f1)
+   CLANG_MINOR  := $(shell $(CXX) -v 2>&1 | awk '{if (NR==1) print $$4}' | cut -d'.' -f2)
+endif
 else
 ifneq ($(findstring gnu,$(COMPILER)),)
 GCC_MAJOR     := $(shell $(CXX) -dumpversion 2>&1 | cut -d'.' -f1)